replace-string-easy.php
<?php function replacestring($search,$replace,$subject) { $srchlen=strlen($search); // lenght of searched string if ($srchlen==0) return $subject; $find = $subject; while ($find = stristr($find,$search)) { // find $search text in $subject - case insensitiv $srchtxt = substr($find,0,$srchlen); // get new search text $find=substr($find,$srchlen); $subject = str_replace($srchtxt,$replace,$subject); // replace founded case insensitive search text with $replace } return $subject; } $a="Hello world, hello world, hello World, HelLo WOrld"; echo replacestring("hello","<b>hello</b>",$a); ?>